Apparatus and methods for systematic non-uniformity correction using a gas cluster ion beam

ABSTRACT

Embodiments of an apparatus and methods for correcting systematic non-uniformities using a gas cluster ion beam are generally described herein. Other embodiments may be described and claimed.

FIELD OF THE INVENTION

The field of invention relates generally to the field of semiconductorintegrated circuit manufacturing and, more specifically but notexclusively, relates to correction of systematic non-uniformities usinga gas cluster ion beam.

BACKGROUND OF THE INVENTION

Gas-cluster ion beams (GCIB's) are used for etching, cleaning,smoothing, and forming thin films. For purposes of this discussion, gasclusters are nano-sized aggregates of materials that are gaseous underconditions of standard temperature and pressure. Such gas clusters mayconsist of aggregates including a few to several thousand molecules, ormore, that are loosely bound together. The gas clusters can be ionizedby electron bombardment, which permits the gas clusters to be formedinto directed beams of controllable energy. Such cluster ions eachtypically carry positive charges given by the product of the magnitudeof the electronic charge and an integer greater than or equal to onethat represents the charge state of the cluster ion.

The larger sized cluster ions are often the most useful because of theirability to carry substantial energy per cluster ion, while yet havingonly modest energy per individual molecule. The ion clustersdisintegrate on impact with the workpiece. Each individual molecule in aparticular disintegrated ion cluster carries only a small fraction ofthe total cluster energy. Consequently, the impact effects of large ionclusters are substantial, but are limited to a very shallow surfaceregion. This makes gas cluster ions effective for a variety of surfacemodification processes, but without the tendency to produce deepersubsurface damage that is characteristic of conventional ion beamprocessing.

Conventional cluster ion sources produce cluster ions having a wide sizedistribution scaling with the number of molecules in each cluster thatmay reach several thousand molecules). Clusters of atoms can be formedby the condensation of individual gas atoms (or molecules) during theadiabatic expansion of high-pressure gas from a nozzle into a vacuum. Askimmer with a small aperture strips divergent streams from the core ofthis expanding gas flow to produce a collimated beam of clusters.Neutral clusters of various sizes are produced and held together by weakinteratomic forces known as Van der Waals forces. This method has beenused to produce beams of clusters from a variety of gases, such ashelium, neon, argon, krypton, xenon, nitrogen, oxygen, carbon dioxide,sulfur hexafluoride, nitric oxide, nitrous oxide, and mixtures of thesegases.

Several emerging applications for GCIB processing of workpieces on anindustrial scale are in the semiconductor field. Although GCIBprocessing of workpieces is performed using a wide variety ofgas-cluster source gases, many of which are inert gases, manysemiconductor processing applications use reactive source gases,sometimes in combination or mixture with inert or noble gases, to formthe GCIB.

Although gas cluster ion beams have been used to correct for variationsin an upper layer of a workpiece, gas cluster ion beams have not beenused to correct non-uniformities caused by tool specific processanomalies that repeatedly affect the output process parameters of a GCIBapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and not as alimitation in the figures of the accompanying drawings.

FIG. 1 is a diagrammatic view of a GCIB processing apparatus.

FIG. 2 is a diagrammatic view illustrating the interaction of a gascluster ion beam apparatus with pre-process metrology and post-processmetrology.

FIG. 3 shows a spectroscopic ellipsometry film-thickness map of an upperlayer on a workpiece.

FIG. 4 is a flowchart describing one embodiment of a method of creatinga systematic error response based on un-modulated gas cluster ion beamdata and averaged post-process parametric data.

FIG. 5 is a flowchart describing one embodiment of a method ofcorrecting for systematic non-uniformities.

DETAILED DESCRIPTION

An apparatus and method for correcting non-uniformities, includingnon-uniformities of an upper layer of an incoming workpiece andsystematic non-uniformities caused by inherent variation in a processtool such as a gas cluster ion beam tool, using a gas cluster ion beamis disclosed in various embodiments. However, one skilled in therelevant art will recognize that the various embodiments may bepracticed without one or more of the specific details, or with otherreplacement and/or additional methods, materials, or components. Inother instances, well-known structures, materials, or operations are notshown or described in detail to avoid obscuring aspects of variousembodiments of the invention. Similarly, for purposes of explanation,specific numbers, materials, and configurations are set forth in orderto provide a thorough understanding of the invention. Nevertheless, theinvention may be practiced without specific details. Furthermore, it isunderstood that the various embodiments shown in the figures areillustrative representations and are not necessarily drawn to scale.

In the description and claims, the terms “coupled” and “connected,”along with their derivatives, are used. It should be understood thatthese terms are not intended as synonyms for each other. Rather, inparticular embodiments, “connected” may be used to indicate that two ormore elements are in direct physical or electrical contact with eachother while “coupled” may further mean that two or more elements are notin direct contact with each other, but yet still co-operate or interactwith each other.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, material, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention, but do not denote that theyare present in every embodiment. Thus, the appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily referring to the same embodimentof the invention. Furthermore, the particular features, structures,materials, or characteristics may be combined in any suitable manner inone or more embodiments. Various additional layers and/or structures maybe included and/or described features may be omitted in otherembodiments.

Various operations will be described as multiple discrete operations inturn, in a manner that is most helpful in understanding the invention.However, the order of description should not be construed as to implythat these operations are necessarily order dependent. In particular,these operations need not be performed in the order of presentation.Operations described may be performed in a different order than thedescribed embodiment. Various additional operations may be performedand/or described operations may be omitted in additional embodiments.

There is a general need for correcting non-uniformities using a gascluster ion beam. By correcting non-uniformities, includingnon-uniformities of an upper layer of an incoming workpiece andsystematic non-uniformities caused by inherent variation in a processtool such as a gas cluster ion beam tool, a more repeatable and constantprocess may be provided.

With reference to FIG. 1, a GCIB processing apparatus 200 includes avacuum vessel 102 divided into communicating chambers that include asource chamber 104, an ionization/acceleration chamber 106, and aprocessing chamber 108 separated from the source chamber 104 by theionization/acceleration chamber 106. The chambers 104, 106, 108 areevacuated to suitable operating pressures by vacuum pumping systems 146a, 146 b, and 146 c, respectively. A condensable source gas 112 (forexample, argon (Ar), carbon dioxide (CO₂), oxygen (O₂), or nitrogen(N₂)) stored in a source gas cylinder 111 is admitted under pressurethrough a gas metering valve 113 and a gas feed tube 114 into astagnation chamber 116. The source gas is subsequently ejected from thestagnation chamber 116 into the substantially lower pressure vacuuminside the source chamber 104 through a properly shaped nozzle 110. Agas jet 118 results inside the source chamber 104. Cooling, whichresults from the rapid expansion of the jet 118, causes a portion of thegas jet 118 to condense into clusters, each consisting of from severalto several thousand weakly bound atoms or molecules.

A gas skimmer aperture 120 situated between the source chamber 104 andionization/acceleration chamber 106 partially separates any gasmolecules that have not condensed into clusters from those that havecondensed and become part of the gas jet 118. The removal of theun-condensed gas molecules minimizes pressure increases in thedownstream regions where such higher pressures would be detrimental,such as in the ionization/acceleration chamber 106 near ionizer 122 andhigh voltage electrodes 126 and in the process chamber 108.

After the gas jet 118 has been formed in the source chamber 104, theconstituent gas clusters in gas jet 118 are ionized by ionizer 122. Theionizer 122 is typically an electron impact ionizer that produceselectrons from one or more filaments 124 and accelerates and directs theelectrons causing them to collide with the gas clusters in the gas jet118 inside the ionization/acceleration chamber 106. The electron impactejects electrons from molecules in the gas clusters to generate ionizedmolecules and thereby endows the gas clusters with a net positive chargeto define cluster ions. A filament power supply 136 provides voltageV_(F) to heat the ionizer filament 124.

A set of suitably biased high voltage electrodes 126 in theionization/acceleration chamber 106 extracts the cluster ions from theionizer 122. The high voltage electrodes 126 then accelerate theextracted cluster ions to a desired energy and focus them to define theGCIB 128. The kinetic energy of the cluster ions in GCIB 128 typicallyranges from 1 thousand electron volts (keV) to several tens of keV.Anode power supply 134 provides voltage V_(A) to at least one of thehigh voltage electrodes 126 for accelerating electrons emitted fromfilament 124 and causing the electrons to bombard the gas clusters ingas jet 118, which produces cluster ions.

Extraction power supply 138 provides voltage V_(E) to bias at least oneof the high voltage electrodes 126 to extract ions from the ionizingregion of ionizer 122 and to form the GCIB 128. Accelerator power supply140 provides voltage V_(Acc) to bias one of the high voltage electrodes126 with respect to the ionizer 122 so as to result in a total GCIBacceleration energy equal to VACC electron volts (eV). Lens powersupplies 142, 144 may be provided to bias some of the high voltageelectrodes 126 with potentials (e.g., V_(L1) and V_(L2)) to focus theGCIB 128. A beam filter 256 in the ionization/acceleration chamber 106eliminates monomers or monomers and light cluster ions from the GCIB 128to define a GCIB 202 that enters the processing chamber 108.

A beam gate 222 is disposed in the path of GCIB 128 in theionization/acceleration chamber 106. Beam gate 222 has an open state inwhich the GCIB 128 is permitted to pass from the ionization/accelerationchamber 106 to the processing chamber 108 to define GCIB 202 and aclosed state in which the GCIB 128 is blocked from entering theprocessing chamber 108. A control cable 224 conducts control signalsfrom dosimetry processor 214 to beam gate 222. The control signalscontrollably switch beam gate 222 to between the open or closed states.

A workpiece 210, which may be a semiconductor wafer or other substrateto be processed by GCIB processing, is disposed in the path of the GCIB202 in the processing chamber 108. Because most applications contemplatethe processing of large workpieces 210 with spatially uniform results, ascanning system may be desirable to uniformly scan the GCIB 202 acrosslarge areas to produce spatially homogeneous results.

The GCIB 202 directed at the workpiece 210 may be substantiallystationary (i.e., un-scanned). Workpiece 210 is held in the processingchamber 108 on a X-Y positioning table 204 operable to move theworkpiece 210 in two axes, effectively scanning the workpiece 210relative to the GCIB 202. The GCIB 202 impacts the workpiece 210 at aprojected impact region 244 on a surface of the workpiece 210. By X-Ymotion, the X-Y positioning table 204 can position each portion of asurface of the workpiece 210 in the path of GCIB 202 so that everyregion of the surface may be made to coincide with the projected impactregion 244 for processing by the GCIB 202. An X-Y controller 216provides electrical signals to the X-Y positioning table 204 through anelectrical cable 218 for controlling the position and velocity in eachof X-axis and Y-axis directions. The X-Y controller 216 receives controlsignals from, and is operable by, system controller 228 through anelectrical cable 226. X-Y positioning table 204 moves by continuousmotion or by stepwise motion according to conventional X-Y tablepositioning technology to position different regions of the workpiece210 within the projected impact region 244. In one embodiment, X-Ypositioning table 204 is programmably operable by the system controller228 to scan, with programmable velocity, any portion of the workpiece210 through the projected impact region 244 for GCIB processing by theGCIB 202.

Alternatively, orthogonally oriented electrostatic scan plates 130, 132can be utilized to produce a raster or other scanning pattern of theGCIB 202 across the desired processing area on workpiece 210, instead ofor in addition to using positioning table 204. When beam scanning isperformed, a scan generator 131 provides X-axis and Y-axis scanningsignal voltages to the scan plates 130, 132. The scanning signalvoltages provided to the scan plates 130, 132 may be triangular waves ofdifferent frequencies that cause the GCIB 202 to scan the entire surfaceof workpiece 210.

The workpiece holding surface 260 of positioning table 204 iselectrically conductive and is connected to a dosimetry processor 214 byan electrical lead 212. An electrically insulating layer 258 ofpositioning table 204 isolates the workpiece 210 and workpiece holdingsurface 260 from the other portions of the positioning table 204.Electrical charge induced in the workpiece 210 by the impinging GCIB 202is conducted through workpiece 210, workpiece holding surface 260, andelectrical lead 212 to the dosimetry processor 214 for measurement.Dosimetry processor 214 has integrating means for integrating the GCIBcurrent to determine a GCIB processing dose. Under certaincircumstances, a target-neutralizing source (not shown) of electrons,sometimes referred to as electron flood, may be used to neutralize theGCIB 202. In such case, a Faraday cup (not shown) may be used to assureaccurate dosimetry despite the added source of electrical charge.

The processing chamber 108 includes optical windows 230 and 232. Anoptical transmitting transducer 234, which may also have additionaltransmitting optics 236, and an optical receiving transducer 238, whichmay also have additional receiving optics 240, form a conventionaloptical instrumentation system. The transmitting transducer 234receives, and is responsive to, controlling electrical signals from thesystem controller 228 communicated through an electrical cable 246. Thetransmitting transducer 234 directs an optical beam through the opticalwindow 230 toward the workpiece 210. The receiving transducer 238detects the optical beam through optical window 232. The receivingtransducer 238 sends measurement signals to the system controller 228through an electrical cable 242.

The optical instrumentation system may comprise any of a variety ofdifferent instruments for tracking the progress of the GCIB processing.For example, the optical instrumentation system may constitute aspectroscopic ellipsometry system for measuring or mapping the thicknessof the upper film layer on the workpiece 210. As another example, theoptical instrumentation system may comprise a scatterometer formeasuring or mapping the thickness of the layer on the workpiecesurface. By operating under control of the system controller 228 and inconjunction with the X-Y positioning table 204, the opticalinstrumentation can map one or more characteristics of the workpiece210.

In addition to gas cylinder 112, the GCIB processing apparatus 200 has asecond gas cylinder 250 for containing a reactive gas 252, which may be,for example, oxygen, nitrogen, carbon dioxide, nitric oxide, nitrousoxide, another oxygen-containing condensable gas, or sulfurhexafluoride. Shut-off valves 246 and 248 are operable by signalstransmitted through electrical cable 254 by system controller 228 toselect either source gas 112 or source gas 252 for GCIB processing.

The dosimetry processor 214 may be one of many conventional dose controlcircuits that are known in the art and may include, as a part of itscontrol system, all or part of a programmable computer system. The X-Ycontroller 216 may include as part of its logic all, or part of, aprogrammable computer system. The dosimetry processor 214 may include aspart of its logic all, or part of, a programmable computer system. Someor all of the logic of the X-Y controller 216 and dosimetry processor214 may be performed by a small general purpose computer that alsocontrols other portions of the GCIB processing apparatus 200, includingthe system controller 228.

In operation, the dosimetry processor 214 signals the opening of thebeam gate 222 to irradiate the workpiece 210 with the GCIB 202. Thedosimetry processor 214 measures the GCIB current collected by theworkpiece 210 to compute the accumulated dose received by the workpiece210. When the dose received by the workpiece 210 reaches a predeterminedrequired dose, the dosimetry processor 214 closes the beam gate 222 andprocessing of the workpiece 210 is complete.

The dosimetry processor 214 is electrically coupled with the systemcontroller 228 by an electrical cable 220. During processing of theworkpiece 210, the dose rate is communicated by the dosimetry processor214 to the system controller 228 by electrical signals transmitted overelectrical cable 220. The system controller 228 analyzes the electricalsignals to, for example, confirming that the GCIB beam flux issubstantially constant or to detect variations in the GCIB beam flux.The X-Y controller 216 is responsive to electrical signals from thesystem controller 228 that are transmitted over an electrical cable 226.The X-Y controller 216 can scan the X-Y positioning table to positionevery part of the workpiece 210 for processing according topredetermined velocities that result appropriate beam dwell times toetch material or to deposit material to the desired local thicknesseseffective to provide a film of substantially uniform thickness.

As an alternative method, the GCIB beam 202 may be scanned at a constantvelocity in a fixed pattern across the surface of the workpiece 210, butthe GCIB intensity is modulated (often referred to as Z-axis modulation)to deliver an intentionally non-uniform dose to the sample. The GCIBintensity may be modulated in the GCIB processing apparatus 200 by anyof a variety of methods, including varying the gas flow from a GCIBsource supply; modulating the ionizer by either varying a filamentvoltage V_(F) or varying an anode voltage V_(A); modulating the lensfocus by varying lens voltages V_(L1) and/or V_(L2); or mechanicallyblocking a portion of the gas cluster ion beam with a variable beamblock, adjustable shutter, or variable aperture. The modulatingvariations may be continuous analog variations or may be time modulatedswitching or gating.

With reference to FIG. 2, the gas cluster ion beam apparatus 200, apre-process metrology tool 420, and a post-process metrology tool 440are configured to communicate with each other and with a host server450. The pre-process metrology and post-process metrology tools 420, 440may be film thickness measurement tools that use spectroscopicellipsometry, scatterometry, interferometry, X-ray fluorescence, andfour point probe techniques. In the embodiment shown in FIG. 2, thepre-process and post-process metrology tools 420, 440 are locatedex-situ of the GCIB processing apparatus 200, which means that themeasurement equipment is located outside the vacuum vessel 102 andseparate from the GCIB processing apparatus 200. In another embodiment,the pre-process and post-process metrology tools 420, 440 are locatedin-situ and, to that end, may be contained within the vacuum vessel 102(FIG. 1) to allow for in-vacuum measurements on the GCIB processingapparatus 200. In yet another embodiment, the pre-process andpost-process metrology tools 420, 440 may be located in-situ outside thevacuum vessel 102 but still considered part of the GCIB processingapparatus 200. The pre-process and post-process metrology tools 420, 440may be separate equipment, if well matched, or they may be the samemetrology equipment.

The pre-process metrology tool 420 and the post-process metrology tool440 may communicate with the GCIB processing apparatus 200 by electricalsignals communicated through a wired interface, such as a SEMI EquipmentCommunications Standard/Generic Equipment Model (SECS/GEM) wiredinterface. A SECS/GEM communication is a wired protocol between a hostserver 450 and the GCIB processing apparatus 200, pre-process metrologytool 420, and post-process metrology tool 440, as well as with othersemiconductor manufacturing tools or equipment (not shown). SECS is alayer 6 protocol that describes the content of the messages while GEM isa higher layer application protocol that defines the messagesthemselves. Alternatively, the wired interface over which the electricalsignals are communicated between the host server 450, GCIB processingapparatus 200, pre-process metrology tool 420, and post-processmetrology tool 440 may be a registered jack (RJ) standardized physicalinterface such an eight-pin Ethernet (8P8C) or two-pin (RJ-11)connector, or a universal serial bus (USB) interface, or an RS-232serial binary data connection.

In one embodiment, a SECS/GEM communication is transferred between thegas cluster ion beam apparatus 200 and the pre-process metrology tool420 over wired communication paths 415 and 455 via server 450. Inanother embodiment, the SECS/GEM communication is transferred betweenthe GCIB processing apparatus 200 and the post-process metrology tool440 through wired communication paths 425 and 455 via server 450. In afurther embodiment, pre-process metrology tool 420 communicates withpost-process metrology tool 440 through wired communication path 415 and425 via server 450.

Alternatively, the GCIB processing apparatus 200 and pre-processmetrology tool 420, and the GCIB processing apparatus 200 andpost-process metrology tool 440 may be coupled in communication usingshort-range wireless technology connections 410, 430, respectively,characterized by respective transceiver interfaces. In one embodiment,the wireless connections 410, 430 may comprise a short-range wirelesstechnology connection to limit interference with other processingequipment, although the invention is not so limited as a long-rangewireless connection may be used in an alternative embodiment.Short-range wireless technologies, such as Bluetooth wirelesstechnology, may communicate data signals over a distance of up to 10meters in a frequency range between 2.402 gigahertz (GHz) and 2.480 GHz.Bluetooth protocols are described in “Specification of the BluetoothSystem: Core, Version 1.1,” published Feb. 22, 2001 by the BluetoothSpecial Interest Group, Inc. Associated, as well as previous orsubsequent, versions of the Bluetooth standard may also be supported bythe wireless connections 410, 430. Alternatively, the short-rangewireless technology, such as ultra-wideband (UWB), may communicatedigital data over a wide spectrum of frequency bands ranging in afrequency range between 3.1 GHz and 10.6 GHz. Other examples of ashort-range wireless technology includes certified wireless universalserial bus (USB), and communications defined by the Institute ofElectrical Institute of Electrical and Electronic Engineers (IEEE)802.11, Wireless Fidelity (Wi-Fi) and IEEE 802.16 WorldwideInteroperability for Microwave Access (WiMAX) suites of standards. IEEE802.11b corresponds to IEEE Std. 802.11b-1999 entitled “Local andMetropolitan Area Networks, Part 11: Wireless LAN Medium Access Control(MAC) and Physical Layer (PHY) Specifications: Higher-Speed PhysicalLayer Extension in the 2.4 GHz Band,” approved Sep. 16, 1999 as well asrelated documents. IEEE 802.11g corresponds to IEEE Std. 802.11g-2003entitled “Local and Metropolitan Area Networks, Part 11: Wireless LANMedium Access Control (MAC) and Physical Layer (PHY) Specifications,Amendment 4: Further Higher Rate Extension in the 2.4 GHz Band,”approved Jun. 27, 2003 as well as related documents.

In one embodiment, parametric data is transferred between the metrologytools 420, 440 and the GCIB processing apparatus 200 to correct fornon-uniformities. According to this embodiment, film thickness mapinformation is fed into the GCIB processing apparatus 200 as aparametric data file. Using a previously measured beam removal functionand a previously measured relationship between etch rate and dose for aparticular set of GCIB parameters (including GCIB energy and clusterspecies), a mathematical algorithm is then employed which takes thenon-uniformity data, inverts beam spot etching pattern to fit thenon-uniformity profile, and creates a beam-dose contour as a systematicerror response to selectively remove surface material and therebyachieve a uniformly thick film. Many different approaches to theselection of mathematical algorithm may be successfully employed in thisembodiment. In another embodiment, the beam-dose contour may selectivelydeposit additional material as a systematic error response on thesurface to achieve a uniformly thick film.

To a first approximation, a beam profile will be a Gaussian function forany cross-section slice of the beam 202 (FIG. 1) in cylindricalcoordinates with the beam propagation axis as the Z-axis of thecoordinate system. For the case of profiling by variations in the beamdwell time, the mathematical inversion and deconvolution that must beperformed are simplified because the response function of the sample islinear with changes in dose. Hence, the beam removal function hasessentially the same mathematical functional shape as the beam intensityprofile. The beam dwell-time map, which directly determines thebeam-scan pattern, must be implemented for each systematically varyingfilm batch if angstrom-scale uniformity is desired. Once processed toGCIB specifications, the uniformity of the workpiece(s) may be examinedeither in-situ or ex-situ and the process finished or refined asappropriate.

According to this embodiment, the GCIB processing apparatus 200 as shownin FIG. 2 has a facility for control of the beam-scan profile by directfeedback from the non-uniformity map data, as established either in-situor ex-situ to the GCIB processing apparatus 200. Further, the in-situmeasurement method may be preferred because it is the most timeefficient method and it permits iteration without exposing the workpiece210 to repeated vacuum/atmosphere cycles.

FIG. 3 illustrates a film-thickness map of a wafer with an upper layercomprising a thin film or layer as measured by spectroscopicellipsometry using a commercially available model UV-1280SE thin filmmeasurement instrument manufactured by KLA-Tencor Corporation. Asapparent from FIG. 3, the thickness of a thin film on a workpiece may bemapped as a function of position.

The initial thickness non-uniformity of an upper film layer on workpiece210 may be characterized ex-situ of the GCIB apparatus 200 byspectroscopic ellipsometry or other suitable conventional techniques.Such techniques can produce a point-by-point film thickness map that maybe reduced to thickness contours (or similar) as shown in FIG. 3.Similarly, an in-situ uniformity-mapping instrument using spectroscopicellipsometry or other suitable conventional film thickness mappingtechniques may be incorporated within the GCIB apparatus 200 (FIG. 1)for guiding a profiling process. In either case, the non-uniformitymeasurements may be stored as a series of thickness points with preciseworkpiece positions by a standard computer. A film measurement methodsuch as spectroscopic ellipsometry is used to map the thickness of onlythe top film layer, independent of variations in workpiece thickness,thickness of underlying films, or surface flatness.

A flowchart is illustrated in FIG. 4 describing one embodiment of amethod of creating a systematic error response based on un-modulated gascluster ion beam data and averaged post-process parametric data. Asystematic error response is used to correct for systematicnon-uniformities of a process tool. Systematic non-uniformities are aresult of inherent variations in a process tool such as a gas clusterion beam tool. In block 500, a plurality of workpieces 210, such aswafers with a similarly situated upper film layer, are collected. In oneembodiment, the plurality of workpieces 210 may be a cassette of waferswith a thin film uniformly applied on a top surface of each wafer usinga deposition processing tool. In block 510, the plurality of workpieces210 are processed using an un-modulated GCIB 202. In this embodiment,each workpiece 210 is processed on the GCIB processing apparatus 200 inan un-modulated manner, at constant beam intensity and at a constantscan speed so that all areas of an upper layer of the workpiece 210receive an equivalent applied dose of cluster ions.

In block 520, post-process parametric data is collected from theplurality of workpieces 210 using a post-process metrology tool. Thepost-process parametric data may be a collection of dielectric filmthickness measurements, metal film thickness measurements, resist filmthickness measurements, resistivity measurements, surface layercontamination measurements, surface roughness measurements, or otherparametric data. In block 530, the post-parametric data is averaged. Inblock 540, systematic non-uniformities are identified based on theaveraged post process parametric data. In block 550, a systematic errorresponse is derived based at least in part on the averaged post-processparametric data. The systematic error response may be formulated atleast in part on the etch rate or deposition rate of the gas cluster ionbeam, non-uniformity map data for a workpiece to be processed, and a gascluster ion beam flux profile wherein a density of ions across adiameter of the gas cluster ion beam is characterized.

FIG. 5 is a flowchart describing one embodiment of a method ofcorrecting non-uniformities based at least in part on a systematic errorresponse. In block 600, incoming parametric data is collected from anupper layer of a workpiece 210. The incoming parametric data may be datacollected using film thickness measurement tools using technologies suchas spectroscopic ellipsometry, scatterometry, interferometry, X-rayfluorescence, and four point resistivity techniques. The incomingparametric data may be measured on a workpiece 210 to be processed by agas cluster ion beam tool 200. In block 610, non-uniformities areidentified in the incoming parametric data. In block 620, a GCIB 202 isdirected toward a surface of the workpiece 210. In block 630, an applieddose from the GCIB 202 is modulated using a systematic error response tocorrect for systematic non-uniformities.

Modulation represents an un-even application of dose to an upper layereither through a change in scan speed of the X-Y positioning table 204as the GCIB 202 traverses the upper layer or through a change inintensity of the GCIB 202. Either method may be used individually or incombination to modulate an applied dose. An applied dose is a measure ofthe amount of material from a GCIB 202 impinging on a workpiece 210 overtime. The material from the GCIB 202 may be incorporated into theworkpiece in some form or it may escape the workpiece in the form of agas or vapor.

To change the scan speed, the X-Y controller 216 (FIG. 1) maneuvers theX-Y positioning table 204 to position every part of the workpiece 210for processing according to predetermined velocities that resultappropriate beam dwell times to etch away or to deposit material to thedesired thicknesses to correct for systematic non-uniformities and toprovide a film of uniform thickness. This is one embodiment formodulating an applied dose of the GCIB 202 (FIG. 1). Alternatively, abeam is scanned at constant velocity in a fixed pattern across thesurface, but the GCIB intensity is modulated (often referred to asZ-axis modulation) to deliver an intentionally non-uniform dose to thesample. This is another embodiment for modulating an applied dose of theGCIB 202. The GCIB intensity may be modulated by any or a variety ofmethods, including for example but not limited to: by varying a gas flowfrom the GCIB source supply; by modulating the ionizer of the GCIBprocessing apparatus 200 either by varying a filament voltage V_(F), orby varying an anode voltage V_(A); by modulating the lens focus byvarying lens voltages V_(L1) and/or V_(L2) in the GCIB processingapparatus 200; or by mechanically blocking a portion of the beam bymeans of a variable beam block, adjustable shutter, or variableaperture. The modulating variations may be continuous analog variationsor time modulated switching or gating.

A plurality of embodiments for correcting non-uniformities, includingnon-uniformities of an upper layer of an incoming workpiece andsystematic non-uniformities caused by inherent variation in a processtool such as a gas cluster ion beam tool, using a gas cluster ion beamhas been described. The foregoing description of the embodiments of theinvention has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. This description and theclaims following include terms, such as left, right, top, bottom, over,under, upper, lower, first, second, etc. that are used for descriptivepurposes only and are not to be construed as limiting. For example,terms designating relative vertical position refer to a situation wherea device side (or active surface) of a substrate or integrated circuitis the “top” surface of that substrate; the substrate may actually be inany orientation so that a “top” side of a substrate may be lower thanthe “bottom” side in a standard terrestrial frame of reference and stillfall within the meaning of the term “top.” The term “on” as used herein(including in the claims) does not indicate that a first layer “on” asecond layer is directly on and in immediate contact with the secondlayer unless such is specifically stated; there may be a third layer orother structure between the first layer and the second layer on thefirst layer. The embodiments of a device or article described herein canbe manufactured, used, or shipped in a number of positions andorientations.

Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the aboveteaching. Persons skilled in the art will recognize various equivalentcombinations and substitutions for various components shown in theFigures. It is therefore intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

1. A method of modifying an upper layer of a workpiece using a gascluster ion beam, the method comprising: collecting parametric datarelating to an upper layer of the workpiece; identifyingnon-uniformities in the parametric data; directing the gas cluster ionbeam toward the upper layer of the workpiece; and spatially modulatingan applied dose, based at least in part on a systematic error responseand the parametric data, of the gas cluster ion beam as a function ofposition on the upper layer of the workpiece to correct thenon-uniformities.
 2. The method of claim 1, wherein the non-uniformitiesare formed by a process performed on the upper layer of the substratebefore the gas cluster ion beam is directed toward the upper layer ofthe substrate.
 3. The method of claim 1, wherein collecting theparametric data further comprises: collecting the parametric data usingan ex-situ metrology tool that is external to a vacuum enclosure of agas cluster ion beam tool in which the gas cluster ion beam is directedtoward the upper layer of the workpiece.
 4. The method of claim 3,wherein the ex-situ metrology tool is selected from the group consistingof a spectroscopic ellipsometer, scatterometer, interferometer, X-rayfluorescence tool, and a four point probe tool.
 5. The method of claim1, wherein spatially modulating the applied dose of the gas cluster ionbeam further comprises: moving the second workpiece relative to the gascluster ion beam with a dwell time at each position determined at leastin part by the systematic error offset.
 6. A method of correctingsystematic non-uniformities using a gas cluster ion beam, the methodcomprising: generating a first data set for each of a plurality ofworkpieces; scanning the gas cluster ion beam without modulation acrossan upper layer; generating a second data set for each of the pluralityof workpieces; identifying systematic non-uniformities in parametricdata generated by comparing a parameter in the first and second datasets of each of the plurality of workpieces; scanning the gas clusterion beam across an upper layer of another workpiece; and spatiallymodulating an applied dose of the gas cluster ion beam as a function ofposition on the upper layer of the another workpiece to correct for thesystematic non-uniformities.
 7. The method of claim 6, scanning the gascluster ion beam without modulation further comprises: exposing theupper layer of the another workpiece to the gas cluster ion beam toinduce the systematic non-uniformities.
 8. The method of claim 6,wherein the first data set comprises pre-gas cluster ion beam processingdata from the plurality of workpieces and the second data set post-gascluster ion beam processing data from the plurality of workpieces. 9.The method of claim 6, wherein at least one of the first data set or thesecond data set is collected using an ex-situ metrology tool.
 10. Themethod of claim 9, wherein the ex-situ metrology tool is selected fromthe group consisting of a spectroscopic ellipsometer, scatterometer,interferometer, X-ray fluorescence tool, and a four point probe tool.11. The method of claim 6, wherein spatially modulating the applied doseof the gas cluster ion beam further comprises: moving the secondworkpiece relative to the gas cluster ion beam with a dwell time at eachposition determined at least in part by the systematic error offset. 12.A processing system for use with a metrology tool, the metrology toolconfigured to map a parameter of an upper layer on each of the processedworkpieces and to generate parametric data representing the mappedparameter, the processing system comprising: a gas cluster ion beamapparatus; and a controller coupled in communication with the gascluster ion beam apparatus and adapted to be coupled in communicationwith the metrology tool, the controller being configured to receive theparametric data from the metrology tool, to generate control signals foroperation of the gas cluster ion beam apparatus that are based upon theparametric data received from the metrology tool, and to communicate thecontrol signals to the gas cluster ion beam apparatus.
 13. Theprocessing system of claim 12, wherein a gas cluster ion beam apparatusincluding a vacuum enclosure, a source configured to produce a gascluster ion beam inside the vacuum enclosure, and a workpiece support inthe vacuum enclosure.
 14. The processing system of claim 13, wherein theworkpiece support includes an X-Y positioning table.
 15. The processingsystem of claim 13, wherein the controller is configured to identifysystematic non-uniformities in the parametric data and to generate thecontrol signals based at least partially on the systematicnon-uniformities for spatially modulating an applied dose of the gascluster ion beam as a function of position on a workpiece supported bythe workpiece support.
 16. The processing system of claim 13, whereinthe gas cluster ion beam apparatus further comprises: a plurality ofscan plates; and a scan generator electrically coupled with the scanplates, the scan generator configured to apply voltages to the scanplates for varying a path of the gas cluster ion beam relative to theworkpiece support.
 17. The processing system of claim 13, wherein thesource is a reactive source.
 18. The processing system of claim 13,wherein the parametric data includes at least one of pre-gas cluster ionbeam apparatus processing data or post-gas cluster ion beam apparatusprocessing data.
 19. The processing system of claim 18, wherein theparametric data comprises film thickness data.
 20. The processing systemof claim 12 wherein the controller communicates with the gas cluster ionbeam apparatus by a first wireless technology connection and isoptionally adapted to communicate with the metrology tool by a secondwireless technology connection.